Container closure with profiled liner

Abstract: The invention provides a liner (4) for a container closure for disposition on the neck of a container (7), said closure comprising crown (1) and a peripherally depending skirt (2), said liner being formed of a resilient material retained on the under side of the crown and being provided at its intended point of abutment with the rim (10) of the container neck (9) on its downwardly directed face with a pair of radially annular ribs (19, 20) for cooperation with the rim of the container neck for with which it is to be used, wherein the pair of concentric annular ribs are disposed adjacent each other with their juxtaposed faces (21) exceeding in width the contact surface of the rim (10) of the container neck with the proviso that the radially inner of said ribs (20) does not comprise an unsupported inclined plane. This arrangement allows for better sealing of container closures, particularly those formed of plastics material such as PET.

Description: The present invention relates to a container closure and profiled liner assembly and particularly such an assembly adapted to alleviate the problem of leakage of gas from containers under pressure. As may be seen from Figures 1A to 2B of the drawings accompanying this Specification closures having profiled liners for disposition upon the neck of a container are known. In particular such prior art closures comprise a crown (1) with a circumferentially depending skirt (2) formed of a plastics material. The outer surface of the skirt (2) is provided with a knurl (3) in order to assist gripping of the closure in use. A profiled liner (4) is disposed on the underside of the crown. In use the neck of a container (7) which is provided with a screw thread (8) and a rim (9) is provided for interengagement with this prior art closure. When the closure is screwed on to the screw thread (8) the contact face (10) of the rim (9) is driven upwardly until it contacts the underside of the profiled liner (4). In the arrangement shown in Figures 1A and 1B the liner is formed in situ from a thermoplastic or a thermosetting material and is retained against separation prior to use within the closure by means of an outer annular rib (14) which acts to retain the profiled liner within the closure and to provide a reservoir of material for sealing purposes against the contact face (10) of the rim (9). Closures of this prior art type may be utilised with plastics or glass containers which are almost always moulded. Although the glass or plastics rim (9) is normally moulded to close tolerances, inevitably some moulded products have discontinuities in their external face and accordingly leakage paths (12), as shown in Figure 1B, allow gas under pressure to escape from containers, e.g. bottles, such as those used for carbonated beverages, particularly if returned for reuse. This happens, for example, particularly when the ambient temperature is raised. In the arrangement shown in Figure 1, the liner material is comparatively hard and this contributes to the possibility that leakage paths (12) will be formed in the event that the container rim is damaged. Further there is a particular problem with closures for plastics (eg PET) containers because the threaded portions associated therewith, are relatively long in the axial direction, thus decreasing the sealing area and increasing the need for effective lateral sealing in the small space left. Further, in such arrangements "top" seal must be particularly effective. An immediate solution to this problem is shown in prior art arrangement Figures 2A and 2B. In these arrangements the profiled liner (4) is formed with a softer compound (16) to provide the excellent seal as shown in Figure 2B. By means of this arrangement partial penetration of the container rim into the liner causes the compound (16) to reform to the shape of the container. The displaced compound then extrudes into the gap between the outer surface of the container and the edge of the retaining lip (5). When unscrewing the closure, the extruded portion may become detached. This means that when the closure is removed there is a possibility that portions of the liner material may find their way into the beverage which the drinker may then reject. Further the scrap portion of the liner (15) when separating from the liner (4) can tear the liner thereby creating leakage paths. For this reason the arrangement of Figures 2A and 2B, although solving the problem of leakage paths (12) in fact creates new problems. A second arrangement as shown in Figures 3A and 3B has also been tried, although not published, wherein the profiled liner (4) is provided with a cutaway outer annular rib (17) having a planar face (18) directed generally inwardly and upwardly as shown in Figure 3A. This has the effect of reducing the amount of displaced compound and this reduces the amount of extruded compound. Consequently the amount of compound in contact with the container is also reduced. This in turn reduces the effectiveness of the side-sealing capability of the liner. Again this allows leakage paths (12) to be developed which, although not so serious as the arrangements of Figures 1A and 1B nevertheless do create a problem. In GB-A-1578489 there is described a liner for a container closure for disposition upon a neck of the container, said closure comprising a crown and peripheral depending skirt, which liner is formed of a resilient material retained on the underside of the crown, the liner being provided on its downwardly directed face with a pair of radially spaced annular ribs for cooperation with the rim of the container neck with which it is intended to utilise the closure. However, the radially inner of said ribs is unsupported in an inclined direction. Such an arrangement is ineffective because there is simply too little material in this asymmetric arrangement to provide for an effective seal. Further there is a tendency for the closures to stop short of a full sealing engagement once a planar face contacts a container neck over some, but not at all, of the container neck rim, so as to leave leakage paths. This drawback is less serious if the planar inclined surface is formed radially outwardly of the inner rib. In US-A-5 060 818, there is disclosed a liner arrangement having two sealing ribs for cooperation with the rim of a container and in WO-A-85/00153 there is disclosed a crown arrangement where a downwardly depending formation therefrom supports an inner side of an annular liner. According to an aspect of the present invention there is provided a container closure and liner assembly, said closure being adapted for disposition upon the neck of the container and comprising a crown and a peripherally depending skirt, said liner being formed of a resilient material retained on the underside of the crown and being provided on its downwardly directed face with at least one annular sealing rib for cooperation with the rim of the container; characterised in that the underside of the crown is provided with at least one downwardly depending formation directly above and in cooperation with said annular sealing rib thereby to support the same in use. Preferably, a pair of radially spaced annular ribs is provided on the underside of the liner, the juxtaposed faces of the ribs exceeding in width a contact surface of the rim of the intended container neck. Conveniently the juxtaposed faces of the ribs have mutually symmetric or asymmetric surfaces whereby, for example, the outer rib surface maybe an inclined plane and the inner rib surface may be convex. The juxtaposed faces of the ribs may be spaced apart at their point of juncture with the liner; said space being adjusted to accommodate the width of the container neck with which the closure is to be used. The ribs when supported may be symmetric or asymmetric and it is desirable that the configuration of the support is formed with the crown to be generally of the same transverse cross section, although smaller, than the sealing rib it supports. Thus it may be asymmetric with an inclined plane or a symmetric convex annulus for example. The term "supported" as used in the specification in association with the downwardly depending formation relates to the effect of the downwardly depending formation on the under side of the crown. This formation may have a cross section which is the same as, or different from, the configuration of the rib. In one embodiment of the invention a notional median line of the intended container neck passes in use through, or immediately adjacent, the point of a juncture of the juxtaposed face of the outer rib with the liner. The liner may be formed in situ on the underside of the crown, or maybe a loose liner disposed in the container closure prior to use, and optionally secured to the underside of the crown adhesively. Container closures containing liners in accordance with the present invention may be provided on the inner face of the skirt adjacent the crown with a radially inwardly directed projection adapted to retain the liner in situ against the underside of the rim. Such a radial projection is preferably configured to retain a distal surface of a radially outer of the annular ribs of the liner in close abutment therewith. Thus the configuration of the radial projection and the distal surface of the outer rib of the liner are preferably arranged to be mutually interengaging. Preferably the distal surface of the liner's outer rib conjoins the closure's radial projection at the point at which the distal surface of the outer rib also conjoins a contact surface of the rib. Preferably, the crown is provided on its underside with two radially spaced downwardly depending formations in register with each of said ribs respectively. These arrangements act to assist in effective manufacture and sealing. The present invention extends to a liner for use in the assembly as defined above. The assembly of the present invention may be formed by a method of forming a liner in situ within a container closure which method comprises; disposing sufficient of a plastics formable material on the underside of the crown of the closure; applying a shaped platen to said plastics material at a predetermined temperature and/or pressure to said so formed assembly and then withdrawing said platen; whereby the platen has an obverse configuration to that of the liner to provide an assembly configuration as defined above. Such a method is particularly effective where at least one of the sealing ribs is supported by an annulus downwardly depending from the crown. The invention will now be described, by way of illustration only, in the accompanying drawings. Figures 1A and 1B show respectively in diagrammatic part section a closure member in accordance with the prior art immediately prior to interengagement (Figure 1A) and after interengagement (Figure 1B); Figures 2A and 2B show a view similar to the arrangement of Figures 1A and 1B except utilising a softer compound for the profiled liner. Figures 1A to 2B are in the prior art; Figures 3A and 3B show a vertical cross section similar to those shown in the previous figures wherein Figure 3A shows a closure immediately prior to interengagement and Figure 3B shows the container closure and container neck in interengagement; Figures 4A and 4B shows an arrangement not in accordance with the present invention but included to assist in the understanding of the invention. The arrangement is shown in vertical cross section. Figure 4A shows the closure about to be interengaged with a container neck and interengaged in Figure 4B; Figures 5A, 5B, 6A and 6B show in vertical cross section embodiments of the invention; and Figures 7A and 7B show a further embodiment in vertical cross section. The prior art has already been discussed with regard to Figures 1A, 1B, 2A and 2B. With reference to Figure 3A a first attempt to solve the problems emanating from the arrangements of Figures 1A and 2A is shown. In this arrangement a cut away annular rib with a planar surface (18) replaces the outer annular rib (14). Although this arrangement solves the problem shown in Figure 2B and limits the amount of scrap liner (15) arising in use and goes some way to disposing of the problems occasioned in Figure 1B by improving the top seal, leakage paths (12) still maybe formed in the case of damaged containers. The arrangements shown in Figures 4A to 5B provide a crown portion formed of a plastics material (1) with a peripheral depending skirt (2), said peripheral depending skirt being provided with a plurality of vertically extending knurls (3) to assist gripping of the closure. The closure is formed with an inwardly directed radial projection (5) spaced downwardly of the crown (1) to locate the liner (4). The closure shown in the Figures 4A to 5B is adapted for cooperation with the neck of a container (7) which neck is provided with a screw thread portion (8) to its exterior, and with a rim (9) adapted to be forced into contact with the profiled liner (4) by operation of the screw thread (8). A notional median line (11) is shown in Figure 4A for purposes to be elucidated later. The rim (9) is provided with a contact surface (10) which should be as smooth and entire as possible having regard to the usual moulding constraints. The rim (9) may be formed of glass, but the invention is particularly effective on plastics beverage containers, for example those formed of PET. The arrangement shown in Figures 4A and 4B resides in the utilisation of a profiled liner (4) provided with an outer concentric rib (19) of an asymmetric inclined plane configuration, and an inner concentric rib (20) of a generally symmetric convex configuration. Each of the ribs (19) and (20) is provided with a juxtaposed face (21), the juxtaposed face of the outer concentric rib being, in this case inclined and planar, whereas the juxtaposed face of the inner concentric rib (21) is convex. The juxtaposed faces (21) are spaced apart by means of a radially spaced portion (22) which may be adjusted to accommodate various widths of container neck (7). It will be noted that the median line (11) although it notionally passes in use through the spaced portion (22) does so in this instance immediately adjacent the point of juncture of the planar juxtaposed face (21) and the spaced portion (22). This arrangement, taken with the planar configuration tends to increase the inwardly directed force on the contact surface (10) of the container rim (9) for the purpose of reducing the possibility of leakage paths (12) forming. The arrangement is shown in its assembled condition in Figure 4B, wherein the container neck (9) has deformed the juxtaposed surfaces (21) of the profiled liner (4) and the spaced portion (22) such that the liner is moulded about the neck of the container thereby reducing significantly the chances of formation of leakage paths (12). It will be appreciated that with the displacement of the material of profiled liner (4) a firm seal is engendered between the liner, the crown, and container neck. Further it will be noted that the material displaced is sufficiently small such that extruded scrap material (15) is not significant. In this instance the liner material is made from a polyolefin/synthetic rubber admixture with a Shore hardness of 55 to 95 or preferably 58 to 75. A similar arrangement is shown in Figures 5A, 5B, 6A and 6B the only differences being the provision of a symmetric annular rib support (13) on the underside of the crown (1) of the container closure and an outer asymmetric/symmetric rib support (25) as shown in Figures 6A and 6B. The outer rib may be as shown with a generally V-shaped configuration, or may be convex as seen from the underside of the crown. Alternatively, the transverse cross-sectional shape of either the inner or outer rib may be asymmetric, e.g. may comprise a planar portion and a convex portion. These arrangements increase the force on the inner contact surface (10) and hence increase the sealing capabilities of the cap while at the same time assisting in manufacture because it allows the thickness of the forming liner material to be kept generally constant over the crown portion of the closure, which prevents formation of voids. Because the thickness of the liner material is kept constant, so differential pressure zones are avoided during the forming of the liner material. Other configurations of the juxtaposed surfaces are envisaged to be both symmetrical or asymmetrical; the precise configuration and width of the spacer portion (22) is selected having regard to the particular requirements of the container closure, its width and the material from which the liner is formed. In a particularly preferred form of the invention the liner is formed of a plastics material selected from non-p.v.c. plastisols conventional in the art. In this respect Figures 7A and B show an arrangement similar to that shown in Figures 4A and 4B wherein the radially outer rib (19) is specially formed such that the inclined plane is formed with a related part (26) of an L-shape in cross section, such that the radially outboard end of the inclined plane (21) remains. This allows a more effective sealing about the outer rim (9) of the container. The invention relates therefore to a container closure and profiled liner assembly with the liner formed loose or formed in situ and configured as above described.

Claims: A container closure and profiled liner assembly, the closure being adapted for disposition upon the neck of the container (7) and comprising a crown (1) and a peripherally depending skirt (2), said liner being formed of a resilient material retained in the underside of the crown, and being provided on its downwardly directed face with at least one annular sealing rib (19, 20) for cooperation with the rim of the container; characterised in that the underside of the crown is provided with at least one downwardly depending formation (13, 25) directly above and in cooperation with said annular sealing rib thereby to support the same in use. An assembly according to claim 1 wherein a pair of radially spaced annular ribs (19, 20) is provided on the underside of the liner, the juxtaposed faces (21) of the ribs exceeding in width a contact surface of the rim of the intended container neck. An assembly according to claim 2 wherein the juxtaposed faces (21) of the ribs have mutually symmetric or asymmetric surfaces. An assembly according to claims 2 or 3 wherein the juxtaposed faces of the ribs are spaced apart at their point of juncture (22) with the liner. An assembly according to claim 4 wherein a notional median line (11) of the intended container neck passes in use through, or immediately adjacent, the point of juncture (22) of the juxtaposed face of the outer rib of the liner. An assembly according to any preceding claim, provided on the inner face of the skirt adjacent the crown with a radially inwardly directed projection (5) adapted to retain the liner in situ against the underside of the crown. An assembly according to claim 6 wherein the radial projection (5) is configured to retain a distal surface of a radially outer of the annular ribs (19). An assembly according to claim 7 wherein the configuration of the projection (5) and distal surface of the outer radially rib (19) are in close abutment, and wherein the distal surface of the outer rib conjoins the radial projection at the point at which the distal surface of the outer rib also conjoins a contact surface (21) of the outer rib. An assembly according to any one of claims 2 to 8 wherein the crown is provided on its underside with two radially spaced downwardly depending formations (13, 25) in register with each of said ribs (19, 20) respectively.

Inventors: THOMPSON NIGEL, THOMPSON, NIGEL
Applicants: METAL CLOSURES GROUP LTD, MCG CLOSURES LIMITED
Application year: 1994
Main classification: B65D41
IPC codes: B65D41